Tutorial 12 — Semiconductors & Electronics

Course: FAD1022 Basic Physics 2
Semester: 2 2025/2026
Centre: Centre for Foundation Studies in Science, Universiti Malaya (PASUM)

Question 1

Sketch the equivalent circuit and determine the current, I for the configurations (a) and (b).

(a) Germanium (Ge) diode with 200 Ω resistor and 5 V supply

(b) Silicon (Si) diode with Germanium (Ge) diode, 250 Ω resistor and 10 V supply

Answers:

  • (a) 0.485 A
  • (b) 0.02 A

Question 2

Two Ge diodes and one Si diode both in forward bias configurations are connected in series to a 10 V direct current power supply, a 20 Ω and a 30 Ω resistors.

Sketch the circuit and determine:

  • Voltage across the 20 Ω resistor — ans: 3.48 V
  • Current passing through the 20 Ω resistor — ans: 0.174 A

Question 3

Given two different half-wave rectifier circuits:

Circuit A:

  • A 15 V peak AC source connected to a silicon diode oriented to conduct only during the positive cycle

Circuit B:

  • A 15 V peak AC source connected to a silicon diode oriented to conduct only during the negative cycle

For both circuits:

a) Sketch the output waveform b) Calculate the peak output voltage, $V_o$ c) Calculate the average DC output voltage

Answers:

  • ii) $V_o = 14.3 \text{ V}$ for both circuits
  • iii) $V_{DC} = 4.547 \text{ V}$ (Circuit A), $V_{DC} = -4.547 \text{ V}$ (Circuit B)

Question 4

For the network below in Figure 4, determine:

Circuit parameters:

  • $V_{CC} = 25 \text{ V}$
  • $R_B = 500 \text{ k}\Omega$
  • $R_C = 3 \text{ k}\Omega$
  • $\beta = 100$

Calculate:

a) Base current, $I_B$ — ans: 48.6 μA b) Collector current, $I_C$ — ans: 4.86 mA c) Collector-emitter voltage, $V_{CE}$ — ans: 10.42 V d) Collector current, $I_C$ if $\beta = 40$ — ans: 1.944 mA e) Collector current, $I_C$ at saturation level — ans: 8.33 mA

Question 5

Given $I_E = 1.0 \text{ mA}$ and $V_{CE} = 10.0 \text{ V}$ for the network in Figure 5.

Circuit parameters:

  • $I_B = 20 \text{ μA}$
  • $R_C = 5.0 \text{ k}\Omega$
  • $R_E = 0.9 \text{ k}\Omega$

Determine:

a) $\beta$ — ans: 49 b) $V_{CC}$ — ans: 15.8 V c) $R_B$ — ans: 710 kΩ

Additional Questions

Question A1

Sketch output waveform for the network below:

  • 6 V supply
  • Ge diode
  • Si diode

Question A2

For network Fig. 1, given $I_B = 50 \text{ μA}$, $I_E = 8 \text{ mA}$ and $V_{CE} = 12 \text{ V}$.

Determine:

a) $I_C$ — ans: 7.95 mA b) $V_{CC}$ — ans: 51.75 V c) $\beta$ — ans: 159 d) $R_B$ — ans: 1021 kΩ @ 1.021 MΩ

Related Concepts

  • Semiconductors & Diodes
  • Transistors & Biasing
  • Semiconductor
  • PN Junction
  • Diode
  • Forward Bias
  • Reverse Bias
  • Half-Wave Rectifier
  • Full-Wave Rectifier
  • BJT
  • Transistor
  • Current Gain ($\beta$)
  • Base Current ($I_B$)
  • Collector Current ($I_C$)
  • Emitter Current ($I_E$)
  • Cutoff
  • Saturation
  • Active Region

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